Three different parameters are being correlated in this research project that seem to influence gingival tissue in normal as well as in pathologic conditions. These are: a) fibrinolysis, b) collagen concentration and c) heparin or heparin-like substances. These parameters are being studied with the intention of tying together some basic fundamental biological phenomena that may interact and play an important role in the connective tissue process. Fibrinolytic activity is being studied by means of Astrup's fibrin plate technique and the Todd's histochemical technique. Differentiation between fibrinolytic and nonspecific proteolytic activity is being determined by using plasminogen-free fibrin plate. Collagen concentration is being determined using a modified Stegeman's micromethod. This technique allows us to quantitate hydroxyproline content in 8 micra microscopic section. Heparin is extracted from gingival tissue by a modified Freed- man's technique and identified microelectrophoretically in agarose (sulphated free) coated microscopic slides. Heparin in the microelectropherotic run is seen as a distinct metachromatic band and is easily distinguished from other mucopolysaccharides by its higher rate of migration. Heparin is quantitated with densitometer by measuring the optical density and comparing with the optical density of a known amount of reference heparin run parallel to the sample being tested in the slide.